Pyrolysis of hydrocarbons with stable high temperature flame



March 3 1965 REIICHI KONDO ETAL 3,176,046

PYRQLYSIS OF HYDHOCARBONS WITH STABLE HIGH TEMPERATURE FLAME Filed Jan. 25, 1961 r 2 Sheets-Sheet 1 FIG.

INVENTORS Rel/CHI Kan/0a KAZUM/ TAKAG/ March 30, 1965 PYROLYSIS OF HYDROCARBONS WITH STABLE HIGH TEMPERATURE FLAME Filed Jan. 25, 1961 REllCHl KONDO ETAL FIG. 3

2 Sheets-Sheet 2 INVENTORS ATTOP/VE 5 3,176,046 PYROLYSKS (if HYDROCARBQNS WITH STABLE HIGH TEMPERATURE FLAME Reiichi Kondo and Kazumi Talragi, Niihama-shi, .l'apan, assignors, by mesne assignments, to Societe lleige de lAzote et des ldroduits Chimiques du Marly, Liege, Belgium, a Belgian company Filed Jan. 25, 1961, Ser. No. 84,856 Claims priority, application Japan, Feb. 3, 1950, 35/234223 4 Claims. (Cl. 26tl--679) This invention relates to the pyrolysis or thermal decomposition of hydrocarbons and, more particularly, to

pyrolysis reactions for producing acetylene and/ or ethylene in a pyrolysis reactor by combustion of fuel gas and oxygen whereby the separately introduced streams of fuel and oxygen impinge at an angle for admixture withing the pyrolysis reactor to form the pyrolyzing flame therein.

As is now well understood, pyrolysis of such materials as petroleum naphtha into unsaturated gaseous hydrocarbons such as acetylene or mixtures of acetylene and ethylene may be accomplished by injection of the hy- United States Patent drocarbon to be pyrolyzed into a pyrolysis reactor within may not be obtained without due consideration to the particular arrangements or circumstances for the mixing and introducing and combustion of the fuel and comburent gases for producing the pyrolysis heat desired.

For example, at adequately high pyrolysis temperatures, acetylene may be almost instantaneously produced by the thermal decomposition of petroleum naphthas, and may be quickly consumed and/or further pyrolyzed into useless carbonaceous products unless the pyrolyzing flame, however intense, is of a very localized extent. Similarly, optimum efliciency may not be obtained without a relatively constantly stable flame front in the pyrolysis reactor resulting from whatever burner or distributor mechanism is utilized for mixing fuel and comburent gases therein. Particularly may this be true in the pyrolysis reactions of the type where the desired end product is formed by thermal decomposition of a hydrocarbon reactant other than the heat-producing fuel, since it is not desired to consume the hydrocarbon reactant, but to decompose it in the heat of the reaction flame and, in a relatively short space of time, quench the resultants at the point of maximum concentration of the desired unsaturated hydrocarbons in the combined gaseous products of the pyrolysis or combustion reaction.

It may also be found that the high temperature or intensity of the flame desired may have a rapidly deleterious effect on the refractory lining of the wal s of the combustion chamber or reactor, and especially if the mixture of fuel gas and cornburent gas results in a positioning or direction of the heat-producing flame so that it impinges upon the refractory reactor walls. Similarly, if the fuel gas and comburent gas are separately injected for admixture into the pyrolysis reaction chamber, maximum thermal efliciency and/or maximum reaction efficiency may not be achieved without careful control and adjustment of the flow rates of the respective gases relative to, for example, the various momenta thereof as correlated with the stoichiometric or combustion proportioning thereof, so that maximum efiiciency may require continued adjustment of the respective flow rates of the gases and/or even replacement of distributor or burner nozzles in the apparatus with those of a different size when, by virtue of commercial circumstances or otherwise, a different fuel gas is used and/or diflerent fiow conditions are desired. 7

According to this invention, by contrast, there is provided for the pyrolysis or thermal decomposition of hydrocarbons into less saturated hydrocarbons (such as acetylene and/ or ethylene) in a pyrolysis reactor utilizing the heat from a combustion flame produced by a fuel gas and a cornburent gas injected into the reactor, and with such injections of fuel gas and comburent gas being controlled to impinge together under such circumstances in the combustion chamber that a stable and high temperature flame is maintained in the apparatus despite pos sible fluctuations in gas volumes or momenta introduced and/or even despite changes in the composition or variety of fuel gas, and, further, that excessive heat loss is avoided and optimum control of the actual pyrolysis reaction is enhanced by providing a fairly short or compressed, though stable, flame for accomplishing the pyrolysis reaction with a minimum of volume in the combustion chamber or reactor and yet without having the heat-producing flame impinge directly or disadvantageously upon the refractory lining of the reactor.

It is, then, with the foregoing and the other objects in view that this invention will be more fully described, and other objects and advantages thereof will be apparent from the following description, the accompanying drawings, and the appended claims.

In the drawing:

FIG. 1 is a somewhat diagrammatic vertical or axial cross section of hydrocarbon pyrolysis reactor apparatus embodying and for practicing this invention;

FIG. 2 is a transverse section of the apparatus of FIG. 1 along the line 11-11 thereof;

FIG. 3 is a somewhat diagrammatic vertical or axial partial section of pyrolysis reactor apparatus embodying and for practicing this invention; and

FIG. 4 is a transverse section of the apparatus of FIG. 3 along the line lV-IV thereof.

Referring to the drawings, in which like reference characters refer to like parts throughout the several views thereof, there is shown pyrolysis reactor apparatus in accordance herewith in which the pyrolysis flame is produced in a combustion chamber by having the fuel or combustion gas and the cornburent gas separately injected in separate streams, with the stream of one of such gases being essentially axial or parallel to the axis of the apparatus and with the stream of the other gas injected to impinge on the first gas stream Within the combustion chamber at an angle within the range of about 1060 to form the desired heat-combustion flame of enhanced stability, of relatively short axial extent, and at a particular point or series of points or locations adequately removed from or insulated against direct impingement on the refractory walls of the combustion chamber or the upper distributor or mixing end thereof through which the gases are injected.

For example, considering FIG. I, a combustion chamber is provided in the apparatus as enclosed within refractory lining 11 and closed at the upper end by a burner member 12 cooled by circulation of coolant through channel 13 as indicated by the inlet 14 and outlet 15 for coolant circulation. An injection nozzle is provided for the injection of oxygen (or air or other comburent gas) into combustion chamber 10 through burner member 12.

Surrounding and spaced from injection nozzle 20 (as noted in FIGS. 1 and 2) is a plurality of inlet nozzles or pipe 21 through burner member 12 with the lower or inner portions 22 thereof radially inwardly inclined so that the streams of fuel gas from the inner portions 22 of nozzles 21 will impinge upon and be mixed with the stream of comburent gas entering combustion chamber 10 through nozzle 20 at an angle within approximately the range of 1060 so as to produce a flame at approximately the position indicated by 25 and spaced from both burner 12 and the surrounding walls 11 of combustion chamber 10. As will be understood, of course, a continuous annular slit, appropriately inclined at the desired angle, produces satisfactory results instead of the plurality of individual fuel gas passages or nozzles 2122.

Also, preferably, a plurality of injection nozzles or an annular slit 26 is provided for injecting into combustion chamber 10 a substantially surrounding and continuous layer or screen of steam between flame 25 and inner refractory walls 11 of combustion chamber 10 to surround and confine the flame as the hot combustion gases from flame 25 and the steam from slit 26 combine and enter the constricted mixing chamber 27 for admixture therein with the hydrocarbon reactant to be pyrolyzed.

The hydrocarbon reactant to be pyrolyzed is introduced at 30 into an annular manifold 31 from which it is injected into mixing chamber 27 through a plurality of injection nozzles (or a continuous annular slit) 32. Preferably annular manifold 31 and injection orifices 32 are cooled as by circulation of water or other coolant through a water jacket indicated at 33 and provided with inlet and outlet connections 34, 35. Preferably, also, for enhanced efficiency, the hydrocarbon reactant to be pyrolyzed is pre-heated prior to injection at high velocity through manifold 31 and orifices 32.

Upon admixture with the steam and hot combustion gases from combustion chamber 10 in mixing chamber 27, the hydrocarbon to be pyrolyzed proceeds into reaction chamber 40 where it is thermally decomposed by the hot combustion gases. Preferably the inner walls 41 of reaction chamber 40 are cooled and/ or covered by a substantially continuous film or screen of water to form a moving wall of water for avoiding deposition or accumulation of carbonaceous reaction products. As illustrated, such moving liquid wall is provided by supplying water through water inlet 42 into an annular basin 43 for overflowing the top of walls 40 through the annular slot 44. As the hydrocarbon to be pyrolyzed passes through reaction chamber 40 admixed with the hot combustion gases and steam produced in combustion chamber 10, the desired pyrolysis reaction occurs, and is satisfactorily arrested at the lower end of reaction chamber 40 by cold quenching water 47, injected from annularly spaced orifices or slit 48 from manifold 49, to which the water is supplied to inlet 50, and the quenched and completed reaction gaseous product is removed from the apparatus through outlet 51 in the lower portion thereof of the apparatus below quenching sprays 47.

Referring to FIGS. 3 and 4, a somewhat larger type of apparatus embodying and for practicing this invention is illustrated. In this embodiment, a somewhat larger combustion chamber 55 is provided enclosed within refractory walls 56 and having a burner or distributor member 57 at the top portion part thereof. Penetrating through burner 57 are a plurality of injection nozzles 60 for injecting the comburent gas into combustion chamber and, in the illustrated embodiment, these injection nozzles are arranged in a substantially circular configuration around the cross section of combustion chamber 55, arranged to inject a stream of comburent gas substantially parallel to the axis of combustion chamber 55, and spaced from each other and from the walls 56 of combustion chamber 55 as indicated in FIGS. 3 and 4.

Surrounding each of the injection nozzles 60 in a substantially circular configuration (which may, indeed, be an annular slit) are a plurality of fuel inlet passages 61 the lower portions 62 of which are radially inwardly inclined with respect to the several injection nozzles 60 so that streams of fuel gas entering combustion chamber 55 through the various fuel injection nozzles 61 will impinge on and admix with the stream of comburent gas entering through nozzles 60 at an angle of approximately within the range of 10-60, as noted, to form a plurality of individual flames 65 spaced below burner member 57 and in a generally circular configuration around the cross section of combustion chamber 55.

As will be understood from the previous description regarding FIGS. 1 and 2, burner member 57 is preferably water cooled with circulation of coolant as through passages 66 therein from inlet 67 to outlet 68. In the illustrated embodiment, steam is preferably supplied through steam inlets 70 into annular manifold '71 to be injected downwardly around the inside of walls 56 of combustion chamber 55, as through slot '72, to combine with the hot combustion gases in combustion chamber 55 formed by the ring or circle of flames 65.

The hydrocarbon reactant to be pyrolyzed is introduced as at into an annular manifold 76, after preferably being pre-heated and at high velocity, from which it enters a mixing zone through a plurality of injection orifices 77 to become admixed with the hot combustion gases and steam from combustion chamber 55. As in the embodiment previously described, a cooling jacket 78 is preferably provided for annular manifold 76 and supplied with coolant as through inlet 79 and outlet 80. As admixed with the hot combustion gases and steam, the hydrocarbon to be pyrolyzed proceeds downwardly through reaction chamber 85, the walls 86 of which are preferably provided with a moving screen of water supplied to an annular reservoir 87 through water inlet 88 to overflow the top of walls 86 through slots 89. As will be understood, with this embodiment as with that of FIGS. 1 and 2, the pyrolysis action, upon completion, is quenched at the lower portion of reaction chamber (not shown) as by transverse spray of cold water, and the gaseous products collected all in known manner.

As further illustrative of this investigation, satisfactory results were achieved, utilizing, particularly, apparatus as indicated in FIGS. 1 and 2, when 10.2 Nm. hr. of oxygen (about 97.5% pure) were injected through nozzle 20, which had a diameter of about 10 mm., at a velocity of about 39.7 m./sec., while 12.0 Nm. /hr. of coal gas was injected from fuel nozzles 21, having an inside diameter of 2.6 mm. and which were located at regular intervals around injection nozzle 20, at the velocity of 84.5 m./sec., and with the fuel injection nozzles 21, or the lower slanted portions 22., thereof, being arranged so that the stream of fuel gas therethrough impinged upon the stream of oxygen through nozzle 20 at an angle of about 25 between the two streams. In this manner, there was satisfactorily obtained a vertical and desirably short combustion flame along the axis of combustion chamber 10 producing a temperature of as much as 3050 C. Into this combustion situation was injected through steam injection arrangement 26, l0.5/l g./hr. of superheated steam at about 800 C.

Into the combined heated combustion gases from the foregoing was injected a hydrocarbon naphtha having a boiling point within the range of 43138 C and preheated to about 600 C, through hydrocarbon inlet 30 at a flow velocity (calculated at the orifices 32) of about 58 m./sec., admixed with steam in the proportions of about 24.0 kg./hr. of naphtha with 7.2 kg./hr. of steam. The pyrolysis of the naphtha took place in reaction chamber 4% at a contact time of about 0.0018 second between interjection through orifices 3t) and quenching at water spray :7, whereby 47.1 Nmfi/hr. of gas (containing 8.7% acetylene and 16.2% ethylene) was obtained. n the foregoing basis, the enhanced yield calculated on the raw material naphtha was 19.8% and 39.7% by weight, respectively, for acetylene and ethylene, or a total yield of useable product of 59.5%. Even after continuous operation for a substantial length of time, there was no noticeable damage of the silicon-carbide refractory line 11 for the combustion chamber 1i and the mixing chamber 27, nor was there a discernible deposition or accumulation of carbonaceous material on the inner walls of reaction chamber 40.

As will be understood from the foregoing, either the combustion gas or the comburent gas may be injected in accordance herewith through either the axially directed or the inclined injection nozzles, the enhanced results hereof being achieved primarily by having the separate gas streams impinge one on another at an angle and by having at least one of the separate gas streams substantially axially directed of the combustion chamber so that a suitable flame of short axial extent is formed and maintained, despite high injection velocity of the gases, substantially axially directed.

Satisfactory results have been achieved in accordance herewith with the velocity of the two gas streams at the outlet of the injection nozzles maintained within a range of 200 m./sec., although Wide variation within these ranges do not appear to inhibit the enhanced efilciency hereoi. Also, as will be understood, considering such flow rate velocities for the gases injected through the axially directed nozzles 26 or 6b or the inclined surrounding plurality of nozzles 22 or 62, a fairly stable flame of high intensity is maintained at the point of admixing or interception of the several gas streams, particularly provided that the inclined nozzles 22 or 62 surround uniformily the axis of the axially directed nozzles or 68 to maintain the flames or 65 each substantially axially directed for maximum eflieiency, intensity of heat production, and avoidance of refractory damage.

Also, with this arrangement of a plurality of separate inclined gas streams surrounding a primary gas stream (whether it is an arrangement such as 20 and 22 of FIGS. 1 and 2 or 60 and 62 of FIGS. 3 and 4), the permissible or allowable diiference in momenta of the streams of the fuel and comburent gases increases substantially, even as adjusted to maintain a desirably stable and desirably short or compressed flame, and substantially no disturbance or inclination of the flame takes place even if the momentum of one gas diifers considerably from that of the other.

Accordingly, among the enhanced advantages achievable in accordance herewith may be noted that the modification or replacement of burners 12 or 57 (or the modification or replacement of the nozzle sizes and configurations therein) is not required even when a ratio of combustion gas to comburent gas or the volume of combustion gas and comburent gas or the kind of combustion gas or comburent gas is changed from time to time, so that, with apparatus in accordance herewith, such normal commercial changes may be made, even in the same apparatus, while still achieving a desirably enhanced efiiciency as compared with, for example, other specialized types of burner apparatus the size or orifices or flow rates of which might have to be fundamentally altered for different fuels or different operating conditions. Also, the configurations in accordance herewith provide for establishing and maintaining the flames somewhat spaced from both the face of the burner members 123 or 57, as well as the inner walls of the combustion chambers ll) or 55,

6 with, of course, desirably increased life and desirably decreased thermal damage thereof.

While this invention has been described and exemplified in terms of its preferred embodiments, those skilled in the art will appreciate thatmodifications can be made without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In the pyrolysis decomposition of a. gaseous hydrocarbon into more unsaturated hydrocarbons in a pyrolysis zone by heat produced by complete combustion of a fuel gas with a comburent gas in a combustion zone preposed to said pyrolysis zone, the method of establishing and controlling a heat-producing flame in said combustion zone at a substantially stationary position therein, which comprises the steps of separately injecting into said combustion zone said fuel gas and said comburent gas in separate gas streams for admixture in said combustion zone, one of said gases being injected in a stream substantially parallel to the axis of said combustion zone, and the other of said gases being injected into said combustion zone in a plurality of gas streams symmetrically disposed around said first-mentioned axially directed gas stream and directed to impinge upon said first-mentioned axially directed gas stream at an angle of about 10-60, and maintaining said heat-producing flame at substantially the point of impingement of said two gas streams.

2. In the pyrolysis decomposition of a gaseous hydrocarbon into more unsaturated hydrocarbons in a pyrolysis zone by heat produced by complete combustion of a fuel gas with a comburent gas in a combustion zone preposed to said pyrolysis zone, the method of establishing and controlling a heat-producing flame in said combustion zone at a substantially stationary position therein, which comprises the steps of separately injecting into said combustion zone said fuel gas and said comburent gas in separate gas streams for admixture in said combustion zone, said comburent gas stream being injected substantially parallel to the axis of said combustion zone, and said fuel gas being injected into said combustion zone in a plurality of gas streams substantially symmetrically disposed around said first-mentioned axially directed gas stream and directed to impinge upon said first-mentioned axially directed gas stream at an angle of about l060, and maintaining said heat-producing flame at substantially the point of impingement of said two gas streams.

3. In the pyrolysis decomposition of a gaseous hydrocarbon into more unsaturated hydrocarbons in a pyrolysis zone by heat produced by complete combustion of a fuel gas with a comburent gas in a combustion zone preposed to said pyrolysis zone, the method of establishing and controlling a heat-producing flame in said combustion zone at a substantially stationary position therein, which comprises the steps of separately injecting into said combustion zone said fuel gas and said comburent gas in separate gas streams for admixture in said combustion zone, said comburent gas stream being injected substantially parallel to the axis of said combustion zone, and said fuel gas being injected into said combustion zone in a plurality of gas streams substantially symmetrically disposed around said first-mentioned axially directed gas stream and directed to impinge upon said first-mentioned axially directed gas stream at an angle of about 10-60, and maintaining said heat-producing flame at substantially the point or impingement of said two gas streams, and said fuel gas being injected in a plurality of individual gas streams surrounding said comburent gas stream and all inwardly directed to impinge thereon at said angle.

4. In the pyrolysis decomposition of a gaseous hydrocarbon into more unsaturated hydrocarbons in a pyrolysis zone by heat produced by complete combustion of a fuel gas with a comburent gas in a combustion zone preposed to said reaction zone, the method of establishing and controlling a heat-producing flame in said combustion zone at a substantially stationary position therein, which comprises the steps of separately injecting into said combustion zone said fuel gas and said comburent gas in separate gas streams for admixture in said combustion zone, one of said gases being injected in a stream substantially parallel to the axis of said combustion zone, and the other of said gases being injected in a plurality of streams substantially symmetrically disposed around said first-mentioned axially directed gas stream and directed to impinge upon said first-mentioned axially directed gas stream at an angle of about l0-60, and injecting steam into said combustion chamber as an axially directed curtain surrounding said flame.

References Cited the Examiner UNITED STATES PATENTS 3/44 Hincke 26()--679 10/56 Pichler et al 260679 4/57 Schutte 260679 11/57 MacQueen 260-679 7/60 Elliott et a1. 260679 5/61 Peclltold et a1. 260-679 9/62 Braconier et al 260679 FOREIGN PATENTS 2/56 Belgium.

ALPHONSO D. SULLIVAN, Primary Examiner.

ABRAHAM RIMENS, Examiner. 

1. IN THE PYROLYSIS DECOMPOSITION OF A GASEOUS HYDROCARBON INTO MORE UNSATURATED HYDROCARBON IN A PYROLYSIS ZONE BY HEAT PRODUCED BY COMPLETE COMBUSTION OF A FUEL GAS WITH A COMBURENT GAS IN A COMBUSTION ZONE PREPOSED TO SAID PYROLYSIS ZONE, THE METHOD OF ESTABLISHING AND CONTROLLING A HEAT-PRODUCING FLAME IN SAID COMBUSTION ZONE AT A SUBSTANTIALLY STATIONARY POSITION THEREIN, WHICH COMPRISES THE STEPS OF SEPARATELY INJECTING INTO SAID COMBUSTION ZONE SAID FUEL GAS AND SAID COMBURENT GAS IN SEPARATE GAS STREAMS FOR ADMIXTURE IN SAID COMBUSTION ZONE, ONE OF SAID GASES BEING INJECTED IN A STREAM SUBSTANTIALLY PARALLEL TO THE AXIS OF SAID COMBUSTION ZONE, AND THE OTHER OF SAID GASES BEING INJECTED INTO COMBUSTION ZONE IN A PLURALITY OF GAS STREAMS SYMMETRICALLY DISPOSED AROUND SAID FIRST-MENTIONED AXIALLY DIRECTED GAS STREAM AND DIRECTED TO IMPINGE UPON SAID FIRST-MENTIONED AXIALLY DIRECTED GAS STREAM AT AN ANGLE OF ABOUT 10*-60*, AND MAINTAINING SAID HEAT-PRODUCING FLAME AT SUBSTANTIALLY THE POINT OF IMPINGEMENT OF SAID TWO GAS STREAMS. 